“According to the Book of Exodus, the Sabbath is a day of rest on the seventh day, commanded by God to be kept as a holy day of rest, as God rested from creation.”
The Jews observed it on Friday evening through Saturday in accordance with their tradition.
Their tradition was because of the commandment given by God. When that obeyed the commandment to remember the Sabbath and keep it Holy, it wasn't because someone decided it was a good idea and we ought to start something pretty cool.
The observance was not official Friday evening. On Friday, they did all the last minute work, cooking, etc. (extra) to get them through the day of rest so no one would work on the Sabbath.
The pharisees had a zillion ridiculous things that they decided what "defined" work. And they equated their "list" as equal to(the same) as the word of God.